Juvenile hormone plays an important role in the reproduction of the mosquito Aedes aegypti, and the rate of its synthesis by the corpora allata is well regulated. In other insect species this regulation is accomplished by neuropeptides. One of them is a recently characterized allatotropin from Manduca sexta, which stimulates juvenile hormone synthesis in adult, but not larval corpus allatum. A peptide homologous to this allatotropin has been isolated from a locust as a stimulator of oviduct contractions. A peptide homologous to this allatotropin has been isolated from a locust as a stimulator of oviduct contractions. This suggests that members of this novel peptide family may play multiple roles in insect reproduction. I have raised antisera against Manduca allatotropin and used them to study its distribution in Manduca and Aedes by HPLC and ELISA. In Aedes a peptide was found that is very similar to, but different from the allatotropin from Manduca. Using immunocytology, this material was detected both in brain neurons with axon terminals in the corpus allatum, as well as in neurosecretory cells in the abdominal ganglia and neurohemal organs associated with these ganglia. Its presence in homologous structures in Aedes and Manduca, as well as its similarity in physico-chemical characteristics to Manduca allatotropin, suggests that this peptide is a homologue of Manduca allatotropin. This is therefore a putative mosquito allatotropin. The specific aims of this research proposal are: (1) To isolate, chemically characterize, and synthetize this putative Aedes allatotropin. (2) To determine its effects on juvenile hormone biosynthesis and oviduct contractions in the mosquito, and the inhibitory effects of antibodies against this peptide on reproduction. (3) To raise specific antisera to the synthetic peptide and use those to study its distribution within the mosquito and identify putative neural and neurohormonal release sites, and to show that it is released from these sites using immunoelectron microscopy. (4) To quantify concentrations of this putative Aedes allatotropin in the hemolymph in relation to the reproductive cycle with a sensitive sandwich immuno assay. Disruption of the interactions of insect neuropeptides with their receptors has been suggested as a target for a novel generation of insecticides. However, until the physiological relevance of these neuropeptides has been established it is very difficult to select any of them for detailed research in this direction. Manipulation of the putative mosquito allatotropin could have deleterious effects on mosquito reproduction. The work proposed here will yield data as to the physiological relevance of this neuropeptide.